648 



SCIENCE. 



[N. S. Vol. IX. No. 227. 



voted to the Passeriformes, -whicli nearly equal 

 in number of species the rest of the class, only 

 a few pages being allotted to even the larger 

 families ; and the various generic groups are 

 mentioned, as a rule, only by their technical 

 generic names. The book is thus evidently not 

 really adapted to beginners, nor Avholly suited 

 to the general reader, though apparently de- 

 signed ' not only for the tyro in ornithology, 

 but also for the traveller or resident in foreign 

 parts interested in the subject.' The wood- 

 cuts that quite fully illustrate the text are, for 

 the most part, excellent, and prepared especially 

 for the work by G. E. Lodge ; others are famil- 

 iar through frequent previous use. Consider- 

 ing the limitation of space imposed for the sub- 

 ject, the author has, perhaps, supplied all that 

 could be rightfully expected, and has certainly 

 shown himself to be ' up to date ' in all of the 

 essentials of his subject. 



J. A. A. 



Experimental Morphology. By Chaeles B. Dav- 

 enport. New York and London, The Mac- 

 millan Company. 1899. Part Second. Pp. 

 228. 



The second part of Davenport's Experimental 

 Morphology that has just appeared deals en- 

 tirely with phenomena of growth. The first 

 volume described the effects of chemical and 

 physical agents upon protoplosm, and it is in- 

 tended to devote the third volume to cell-di- 

 vision and the fourth to differentiation. The 

 author states that it is the aim of this series 

 ' so to exhibit our present knowledge in the 

 field of experimental morphology as to indi- 

 cate the direction for further research.' 



The present volume gives a clear, brief state- 

 ment of what is known in regard to growth in 

 plants and animals. Slost of the illustrations are 

 taken from plant physiology, and it may, there- 

 fore, be questioned whether a zoologist is in 

 position to summarize so large and important a 

 field of botanical research, but in justification it 

 should be stated that Davenport has attempted 

 to deal with the subject from a common biolog- 

 ical standpoint. 



In reading this volume one cannot fail to be 

 impressed by the enormous difference in our 

 knowledge of growth-phenomena in plants and 



animals. The subjects dealt with cover one of 

 the most interesting fields of biological study — 

 the responses of organisms to their surround- 

 ings and the relation of these responses to the 

 conditions of life under which the form is liv- 

 ing or has lived in the past. The introductory 

 chapter is intended to give an idea of normal 

 growth. Organic growth is defined as increase 

 in volume — ' it is not development, not differen- 

 tiation and not increase in mass.' A broad defi- 

 nition of this sort, while convenient to include 

 a large number of changes resulting in ' an in- 

 crease in volume,' may lead to diflBculties if an 

 attempt is made to find a common explanation 

 of all the phenomena included in the definition, 

 for the processes that take place in plants and 

 animals that produce an increase in volume 

 may be entirely different in their nature. The 

 author has skillfully avoided this pitfall in most 

 cases, although at times one cannot but feel 

 that a most heterogeneous collection of facts 

 has been included in the same category. 



The first chapter (XI.) deals with the effects 

 of chemical agents on growth, and gives in com- 

 pact form a large amount of useful information. 

 In most cases the action of the substance seems 

 to be purely physiological and only secondarily 

 formative. It is not obvious why so much 

 space should be given to pure plant physiology. 

 It is, no doubt, difficult to draw the line between 

 substances that act as foods and others that 

 produce growth, since the latter often (but not 

 always) depend on the former. 



An admirable account of the role of water in 

 growth is given in Chapter XII. Here the au- 

 thor has some new facts that bear on the 

 problem. In the next chapter, dealing with the 

 effect of density of the medium on growth, the 

 results are summed up as showing that ' the 

 diminution or growth is proportional to the 

 osmotic action of the medium.' It is possible, 

 however, that the effect is due also, in part, to 

 the direct injurious action of the salts used to 

 increase the density of the fluids. If due to 

 osmotic action alone, then, the results that fol- 

 low when different substances are used should 

 be in proportion to their osmotic equivalents, 

 but the few facts that are given do not entirely 

 support this general conclusion. 



In Chapter XIV. the effect of molar agents is 



